Can you share a code snippet or public page? It sounds like the application is not being set correctly regarding the 401 issue.
As for the button: this is just an HTML button, and you can change the text of it any way you like. You can see it in the code snippet here: https://developer.squareup.com/docs/payment-form/payment-form-walkthrough#112--add-an-html-div, the text is “Pay $1.00”, but this is just an example - you can change that to be whatever you like.
As for the $1.00 charge on the server-side, again, this is something you can make it to be whatever you want. The CreatePayment request takes in an integer amount, so if you want to figure out the cost of an item, for example, you could call the Catalog API, pull the item and its cost, and pass in the amount instead of 100.